This invention is related to a machining process and particularly to an electrical discharge machining (EDM) technique and tooling.
EDM is a well-known and widely used machining technique. It operates through the erosion of a workpiece, generally metallic, through electrical discharges from an electrode. The process takes place in the presence of a liquid dielectric fluid, such as de-ionized water. An electrode in the shape of an elongated rod, thin wire, or shaped article is put into close contact with the workpiece. Through an electrical potential difference, arcing occurs between the workpiece and the electrode which causes erosion of the workpiece material in a desired manner.
EDM processes are used in numerous machining applications. It is especially desirable for its high forming accuracy, ability to machine extremely hard workpieces, low applied loading of the workpiece, and for deep bores in workpieces.
There are various machining projects which pose difficulties in using EDM processes. For example, due to the workpiece configuration, it may be difficult to provide a continuous stream of dielectric fluid at the machining site. An absence of the fluid interrupts the EDM process. This problem may arise in numerous instances. For example, in a case where a small counter bore is to be formed, a larger bore of a limited depth in the workpiece is generally first formed. Thereafter, when it is desired to continue the bore at a smaller diameter, it may be difficult to provide a flow of dielectric fluid at the machining site. In a more specific example, in the machining of internal combustion engine fuel injection nozzles, it may be desirable to provide a stepped bore of this nature. A dielectric fluid stream flowing over the surface of the nozzle may not properly flow into the machining gap. The EDM tools and techniques in accordance with this invention are intended to address this difficulty.
In accordance with the teachings of this invention, several embodiments of alternate means for directing the flow of dielectric fluid are described. In one embodiment, an air stream jet is directed at an angle from the direction of dielectric fluid flow which disperses the dielectric fluid and forces it into the machining gap. In a second embodiment, the dielectric fluid is atomized with air and the mixture is thereafter sprayed into the machining gap. In a third embodiment, an ultrasonic generator is used to disperse the dielectric fluid which more readily flows into the machining gap.
Additional benefits and advantages of the present invention will become apparent to those skilled in the art to which the present invention relates from the subsequent description of the preferred embodiment and the appended claims, taken in conjunction with the accompanying drawings.